Light and electron microscopy along with histochemistry and electron histochemistry will be used to study the innervation of the lung. Rat fetuses and infants will be used for studies which will utilize histological and histochemical techniques as well as electron microscopy to elucidate the pattern of development of the pulmonary innervation. Denervation degeneration experiments will be used to trace the sensory intrapulmonary innervation and its pathways through the vagus and nodose ganglia. The anatomical and physiological effects of denervation by nerve stripping at the hilum and total denervation by lung excision and reimplantation will be compared in a species such as rabbit or dog. Mapping of the pulmonary innervation by histological and histochemical methods will be done for control information on the species which proves most practical for the denervation experiments. Electron microscopy of the adult rat and Rhesus monkey lung will be continued to study the ultrastructural details of the pulmonary nerves, their endings, and their relationships to effector cells such as smooth muscle and glands as well as sensory receptors. An attempt to study the effects of chronic bronchial obstruction on the pulmonary innervation and smooth muscle will be carried out in the same species used for the denervation studies.